The Milky Way Stole Its Cosmic Neighbors from Another Galaxy

An artist's depiction of simulations used in the research.
An artist's depiction of simulations used in the research. (Image credit: Ethan Jahn, UC Riverside)

Looks like the Milky Way filched from one of its neighbors in the ancient past.

Our home galaxy stole several dwarf galaxies that used to belong to the Large Magellanic Cloud (LMC), a galaxy near the Milky Way. And it all happened because of an ongoing merger between these galaxies, which is a common process in our universe.

The discovery of the theft came courtesy of new data from the Gaia space telescope, an ongoing European mission that will precisely measure the movements of a billion stars all told. Those observations include data about the current movements of several nearby galaxies. 

Related: 3D Map of the Milky Way Is the Best Yet of Its Warped, Twisted Shape

So a team of researchers compared that information with simulations that played out these movements over long periods. The comparison suggested that four ultrafaint dwarfs and two other dwarf galaxies (known as Carina and Fornax) used to be part of the LMC. But the Milky Way, a larger galaxy, managed to tear the LMC apart with its more powerful gravitational field.

In cosmic terms, the theft didn't happen all that long ago. The galaxies came over to the Milky Way's side only about 1 billion years ago, a mere fraction of the 13.8 billion-year age of the universe.

"If so many dwarfs came along with the LMC only recently, that means the properties of the Milky Way satellite population just one billion years ago were radically different, impacting our understanding of how the faintest galaxies form and evolve," lead author Laura Sales, an astronomer at the University of California, Riverside, said in a statement.

Results of the study were published Sept. 5 in the Monthly Notices of the Royal Astronomical Society.

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Elizabeth Howell
Staff Writer, Spaceflight

Elizabeth Howell (she/her), Ph.D., is a staff writer in the spaceflight channel since 2022 covering diversity, education and gaming as well. She was contributing writer for Space.com for 10 years before joining full-time. Elizabeth's reporting includes multiple exclusives with the White House and Office of the Vice-President of the United States, an exclusive conversation with aspiring space tourist (and NSYNC bassist) Lance Bass, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, flying parabolic, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, "Why Am I Taller?", is co-written with astronaut Dave Williams. Elizabeth holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, a Bachelor of Journalism from Canada's Carleton University and a Bachelor of History from Canada's Athabasca University. Elizabeth is also a post-secondary instructor in communications and science at several institutions since 2015; her experience includes developing and teaching an astronomy course at Canada's Algonquin College (with Indigenous content as well) to more than 1,000 students since 2020. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday. Mastodon: https://qoto.org/@howellspace